Given an integer (signed 32 bits), write a function to check whether it is a power of 4.
Example:
Given num = 16, return true. Given num = 5, return false.
Follow up: Could you solve it without loops/recursion?
先说明用循环：
如下
class Solution { public: bool isPowerOfFour(int num) { if(num<1)return false; char position=-1; int i=0; while(i<=31) { if(num&(1<<(i))) { if(-1!=position&&position!=i) return false; position=i; } ++i; } if(position%2)return false; else return true; } };
然后我发现题目中提示，你可以不用循环或者递归吗？我就去搜寻了一下这个题目发现http://www.cnblogs.com/grandyang/p/5403783.html
发现第三种方法很巧妙
原文：http://www.cnblogs.com/csudanli/p/5890604.html